Ultrasonic hair curling device

ABSTRACT

An ultrasonic hair curling device capable of applying ultrasonic vibration efficiently to hairs for effective hair styling in a short time. The device includes a housing, an ultrasonic generator incorporated in the housing for generating ultrasonic vibrations, and a horn connected to receive and transmit the ultrasonic vibrations. The horn is formed at its end with a hollow barrel which projects from the housing for receiving therearound a strand of hair to be curled. The hollow barrel is provided at a portion intermediates at its longitudinal ends with a hair winding zone of which cross-section is smaller than the other portion of the hollow barrel. The hair winding zone of the reduced cross section can vibrate at an amplitude larger than at the front end of the barrel for applying the ultrasonic vibrations efficiently to the hair and making the hair curling effectively.

TECHNICAL FIELD

The present invention is directed to an ultrasonic hair curling device,and more particularly to the ultrasonic hair curling device for curlingthe hair into coils or spirals by application of ultrasonic vibrations.

BACKGROUND ART

A hair curling device for curling the hair by application of ultrasonicvibrations is disclosed in Japanese Laid-Open Publication No. 8-299046.The device includes a hollow barrel which is formed at one end of a horntransmitting ultrasonic vibrations and around which the hair is wound,so that a hair curling is made by the ultrasonic vibrations transmittedthrough the barrel. However, in spite of that a hair winding portion ismade hollow in order to increase the vibration, a maximum amplitude ofvibration occurs at the end of the hollow barrel. Therefore, the middleportion of the barrel actually receiving the hair therearound will notgive sufficient ultrasonic vibrations to the hair, resulting in a lowenergy transmission.

DISCLOSURE OF THE INVENTION

The present invention has been accomplished in order to reduce the aboveproblem and has an object of providing an ultrasonic hair curling devicewhich is capable of efficiently applying the ultrasonic vibration from alimited ultrasonic energy for attaining the effective hair curling in ashort time.

The ultrasonic hair curling device in accordance with the presentinvention includes a housing, an ultrasonic generator incorporated inthe housing for generating ultrasonic vibrations, and a horn connectedto receive and transmit the ultrasonic vibrations. The horn is formed atits end with a hollow barrel which projects from the housing forreceiving therearound a strand of hair to be curled. The main feature ofthe present invention resides in that the hollow barrel is provided at aportion intermediates at its longitudinal ends with a hair winding zoneof which cross-section is smaller than the other portion of the hollowbarrel. The hair winding zone of the reduced cross section can vibrateat an amplitude larger than at the front end of the barrel for applyingthe ultrasonic vibrations efficiently to the hair and making the haircurling effectively.

The hair winding zone may be configured to have a cross-section which issmaller towards a lengthwise center of the hair winding zone than atopposite lengthwise ends of said hair winding zone, or to have a uniformcross-section over its full longitudinal length thereof.

Also, the hair winding zone of reduced cross-section can be realized bya recess formed in an outer surface, an inner surface, or both surfacesof the hollow barrel.

Further, the hair winding zone of reduced cross-section can be realizedby provision of a plurality of slits which extend in the axial directionof the hollow barrel and which are spaced circumferentially around thehollow barrel. Defined between the circumferentially spaced adjacentslits are reeds which vibrate in a radial direction as well as in thelengthwise direction of said hollow barrel. Each slit has such a lengththat causes the reeds to vibrate around at a resonant frequency of saidhorn when the strand of hair is wound around the hair winding zone.Whereby, the hair winding zone can develop radial vibrations, inaddition to having increased the vibration amplitude, for attaining haircurling at an improved efficiency.

The slits have such a length that causes the reeds to vibrate at afrequency higher than the resonant frequency of the horn under a no loadcondition where the hair winding zone receives no strand of hair.

The hollow barrel may be formed along its length with a plurality ofslit groups each composed of the circumferentially spaced slits barrelso that the hair winding portion can extends over a long distance withinthe length of the barrel without substantially lowering a strength ofthe barrel. The slits may be arranged in a manner that the slits in oneslit group are longitudinally aligned with the slits in the adjacentslit group, or the slits in one slit group are staggered in thecircumferential direction with respect to the slits in the adjacent slitgroup.

In order to avoid the slit from having at the corners thereof an originof fracture due to stress concentration, each slit is configured to haverounded corners. In addition, each slit may have its peripherysurrounded by a reinforcement frame which gives an additional thicknessto said periphery of the slit.

Further, the hollow barrel may be additionally formed at its front endwith a plurality of open slits. The open slits extend in the lengthwisedirection of the hollow barrel and are spaced circumferentially aroundthe hollow barrel to define additional reeds between thecircumferentially adjacent open slits, which additional reeds can applyradial vibrations for more improved hair curling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an ultrasonic hair curling device inaccordance with one embodiment of the present invention;

FIG. 2 is a front view of an hollow barrel at one end of a horn employedin the above device;

FIG. 3 is an explanatory view illustrating amplitude distribution alongthe axial direction of the hollow barrel;

FIGS. 4, 5, and 6 are front views of other hollow barrels which may beemployed in the above ultrasonic hair curling device;

FIG. 7 is a front view of another hollow barrel which may be employed inthe above ultrasonic hair curling device;

FIG. 8 is a cross section taken along line 8—8 of FIG. 7;

FIG. 9 is an explanatory view illustrating amplitude distribution alongthe axial direction of the hollow barrel of FIG. 7;

FIGS. 10 and 11 are front view of still other hollow barrels which maybe employed in the above ultrasonic hair curling device; and

FIGS. 12A, 12B, and 12C are sectional views of reinforcement framesadapted around the periphery of a slit in the above hollow cylinder.

BEST MODES FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, there is shown an ultrasonic hair curling device inaccordance with one embodiment of the present invention which includes ahousing 10 accommodating therein an ultrasonic vibrator 20. Connected tothe ultrasonic vibrator 20 is a horn 30 from which a hollow barrel 40projects for winding a strand of hair H therearound. The vibrator 20includes a pair of piezoelectric elements 22 on opposite sides of anelectrode plate 21 and is held between the horn 30 and a fixture 31. Thefixture 31 has a bolt 34 which penetrates through the vibrator 20 and issecured to the rear end of the horn 30 for securing the vibrator 20 tothe horn 30. The vibrator 20, upon receiving a high frequency electricsignal from a driver circuit 23, generates an ultrasonic vibration alongan axis of the horn and transmits the same to the horn 30. The horn 30is made of a metal such as a titanium, aluminum, and stainless steel, orFRP (fiber-reinforced plastic) and is caused by the vibrator 20 tovibrate at a frequency of 20 kHz to 100 kHz.

The horn 30 is composed of a main body 32 received in the housing 10 andthe hollow barrel 40 of circular cross-section projecting concentricallyand outwardly of the housing through a cone 35. The cone 35 is of solidstructure having a diameter smaller towards the hollow barrel 40 so asto amplify the vibration. A flange 33 formed between the main body 32and the cone 35 is retained at the front end of the housing 10 forsecuring the horn 30 to the housing 10. The horn 30 is made into aunitary structure including the main body 32, flange 33, cone 35 andhollow barrel 40. Alternately, the hollow barrel 40 may be formed tohave the flange 33 or the cone 35 an integral part thereof so as to becoupled to the main body 32 by a bolt extending through the inner bottomof the hollow barrel 40.

The main body 32 is given such an axial length that the an axial lengthbetween the center of the vibrator 20 and the flange 33 is equal to λ/2(where λ=wavelength of the ultrasonic vibration) to form a node ofvibration at the flange 33 seeing zero amplitude of vibration.

An axial length from the flange to the front end of the hollow barrel 40is set to be λ/4. When the horn 30 is made of aluminum and is driven togive the ultrasonic vibration at 27 kHz, the length (λ/4) from theflange 33 to the front end of the hollow barrel 40 is about 50 mm. Whenthe horn 30 is made of titanium and is driven to give the ultrasonicwave of the same frequency, the length (λ/4) is 48 mm. The lengthbetween the flange 33 and the front end of the hollow barrel 40 may beset to be 3λ/4 other than λ/4, as necessary.

As shown in FIG. 2, the hollow barrel 40 is formed in its axial centerwith a hair winding zone 41 of which cross-section is smaller than theother portion of the barrel. This hair winding zone 41 is given byprovision of a recess in the outer surface of the barrel to have thecross-section which is made smaller towards the center than at theopposite ends thereof Thus, the hair winding zone 41 of reducedcross-section is given an increased ultrasonic vibration than the otherportion, as indicated by solid lines of FIG. 3, thereby applying theultrasonic vibration efficiently to the strand of the hair at theportion where the hair is wound and therefore enabling to finish thehair styling in a short time. Phantom lines of FIG. 3 show the amplitudeof vibration in the absence of the hair winding zone. As shown in thefigure, the provision of the hair winding zone 41 of reducedcross-section increase a maximum amplitude of vibration than otherwise.It is also made that a distal region 42 forwardly of the hair windingzone 41 is made to have a cross-section smaller than that of the cone 35ranging from the hair winding zone 41 to the flange 33, in order to givea larger amplitude of vibration at the distal region 42 where the hairis possible wound.

As shown in FIG. 4, the hair winding zone 41 may be configured to have auniform cross-section along the axial length thereof. In this version,the distal region 42 serves as an effective stopper for preventing thehair from slipping off the barrel.

Further, the reduction of the cross-section for the hair winding zone 41can be made by, other than the above structure, forming the recess inthe inner surface of the hollow barrel 41, or forming the recesses inthe outer and inner surfaces of the hollow barrel, as shown in FIGS. 5and 6. In order to positively hold the strand of the hair wound aroundthe hair winding zone 41, a hair clamp of known structure can be made.In this case, the flange 33 forming the node of vibration is bestutilized to pivotally support the hair clamp. Any other hair holdingstructure can be adapted to the present invention.

FIGS. 7 and 8 illustrate another embodiment of the present invention inwhich the hollow barrel 40 is formed in its axial center with aplurality of circumferentially spaced slits 50 in order to provide thehair winding zone 41 of the reduced cross-section. Formed between theadjacent ones of the circumferentially spaced slits 50 are reeds 51which vibrate in the radial direction as well as in the axial direction,for improving the hair curling. As shown in FIG. 9, it is also made inthe present invention to give a larger amplitude of vibration (indicateby a solid line) at the hair winding zone 41 than at the distal region21 and to have a maximum amplitude of vibration larger than in the case(indicate by dotted lines) where no slit is formed. The amplitude ofvibration illustrated in the figure is a sum of the amplitude ofvibrations in the axial direction and in the radial direction.

A length L of slit 50 is selected so that the reeds 51 vibrate at aresonant frequency of the horn 30 in a loaded condition where the hairwinding zone 41 receives the strand of the hair and vibrate at afrequency higher than the resonant frequency in a no-load condition, andis determined by the following equation:$L^{2} = {\frac{k^{2}}{2\pi \quad f}\sqrt{\frac{E \cdot I}{\rho \cdot A}}}$

wherein k is a vibration coefficient, ƒ is a vibration frequency (Hz), Eis a vertical compliance (Pa), I is a secondary moment (m⁴), ρ is aspecific gravity (kg/m³), and A is a cross-section (m²) of a single reedbetween the slits. The vibration coefficient k may be selected from aprimary vibration coefficient (k=4.730), a secondary vibrationcoefficient (k=7.853), or a third vibration coefficient depending uponthe length L (λ/4 or 3λ/4) from the flange 33 to the front end of thehollow barrel 40. In this embodiment, the length L is set to be about 11mm.

As shown in FIG. 10, it is equally possible to provide more than onearray of the circumferentially spaced slits along the axial direction inorder to widen the hair winding zone 41. In this case, the slits 50 orreeds 51 in one array are preferred to be staggered with respect to theslits or reeds in the adjacent array for maintaining a strength of thehollow barrel 40. When more than one array of the slits are formed, thehollow barrel 40 may have a length L=3λ/4.

FIG. 11 shows a modification in which a plurality of circumferentiallyspaced open slits 60 are formed in the distal region 42 to giveadditional reeds 61 between the adjacent open slits 60. In this case,the additional reeds 61 capable of vibrating in the axial directionmakes it possible to treatment of the hair even at the distal area 42.The open slit 60 has a length which is determined by the above equationfor the slit 50, but is smaller than that of the closed slit, as shownin the figure because of that the additional reed 61 acts as acantilevered beam to reduce the vibration coefficient k. In thisinstance, the vibration coefficient may be selected from a primaryvibration coefficient (k=1.875), a secondary vibration coefficient(k=4.964) or a third vibration coefficient (k=8.885) depending upon thelength of the hollow barrel 40.

It is noted here that the slit is preferred to have rounded corners inorder to avoid stress concentration thereat. Further, as shown in FIGS.12A to 12C, a reinforcement frame 52 may be formed around at least oneof the outer and inner perimeters of the slit 50, in order to give anadded thickness to the perimeter of the slit, while keeping the reducedcross-section of the hair winding zone.

Although the above embodiments shows the slits which are aligned in theaxial direction of the hollow barrel, the slits may be inclined withrespect to the axial direction at an angle of suitable range.

What is claimed is:
 1. An ultrasonic hair curling device comprising: ahousing; an ultrasonic generator incorporated in said housing forgenerating ultrasonic vibrations; a horn connected to receive andtransmit said ultrasonic vibrations, said horn including a hollow barrelwhich projects from said housing for receive therearound a strand ofhair to be curled; wherein said hollow barrel is provided at a portionintermediate its longitudinal ends with a hair winding zone of whichcross-section is smaller than the other portion of said hollow barrel.2. The ultrasonic hair curling device as set forth in claim 1, whereinsaid hair winding zone is configured to have a cross-section which issmaller towards a lengthwise center of said hair winding zone than atopposite lengthwise ends of said hair winding zone.
 3. The ultrasonichair curling device as set forth in claim 1, wherein said hair windingzone has a uniform cross-section over its full longitudinal lengththereof.
 4. The ultrasonic hair curling device as set forth in claim 1,wherein said hair winding zone of reduced cross-section is realized by arecess formed in at least one of outer and inner surfaces of said hollowbarrel.
 5. The ultrasonic hair curling device as set forth in claim 1,wherein said hair winding zone of reduced cross-section is realized byprovision of a plurality of slits which extend in the axial direction ofsaid hollow barrel and which are spaced circumferentially around saidhollow barrel to define between the circumferentially adjacent slitsreeds which vibrate in a radial direction as well as in the lengthwisedirection of said hollow barrel, each of said slits having such a lengththat causes said reeds to vibrate around at a resonant frequency of saidhorn when the strand of hair is wound around said hair winding zone. 6.The ultrasonic hair curling device as set forth in claim 5, wherein saidslit has such a length that causes said reeds to vibrate at a frequencyhigher than the resonant frequency of said horn in a no load conditionwhere said hair winding zone receives no strand of hair.
 7. Theultrasonic hair curling device as set forth in claim 5, wherein aplurality of slit groups each composed of said circumferentially spacedslits are formed in said hollow barrel along the length thereof, theslits in one slit group being longitudinally aligned with the slits inthe adjacent slit group.
 8. The ultrasonic hair curling device as setforth in claim 5, wherein a plurality of slit groups each composed ofsaid circumferentially spaced slits are formed in said hollow barrelalong the length thereof, the slits in one slit group being staggered inthe circumferential direction with respect to the slits in the adjacentslit group.
 9. The ultrasonic hair curling device as set forth in claim5, wherein each of said slits is configured to have rounded corners. 10.The ultrasonic hair curling device as set forth in claim 5, wherein eachslit has its periphery surrounded by a reinforcement frame which givesan additional thickness to said periphery of the slit.
 11. Theultrasonic hair curling device as set forth in claim 5, wherein saidhollow barrel is additionally formed at its front end with a pluralityof open slits which extend in the lengthwise direction of the hollowbarrel and open at the front end, said open slits being spacedcircumferentially around said hollow barrel to define additional reedsbetween the circumferentially adjacent open slits, said additional reedsvibrating in the radial direction as well as in the lengthwise directionof said hollow barrel.